1. Field of the Invention
This invention relates broadly to battery operated fluid pumps. More particularly, this invention relates to a battery operated fluid pump contained in a spray head.
2. State of the Art
Many household and industrial products are sold in containers that include a sprayer. These products include cleansers, insecticides, polishes, waxes, etc. There are several kinds of sprayers used with these products. Perhaps the most common is the manual push button or trigger operated pump which is seen most frequently on liquid cleansers. It has the advantage of being environmentally friendly (i.e. it does not require a propellant) but the disadvantage of delivering fluid in a series of pulses rather than in a continuous spray. Another well known sprayer is the aerosol can which is sealed and charged with a gas propellant. This sprayer has the advantage that it dispenses fluid in a continuous spray, but has several disadvantages. One disadvantage is that the can cannot be refilled. Another disadvantage is that depending on the gas used to charge the container, the propellant can be environmentally unfriendly. While environmentally friendly propellants do exist, generally, they do not charge as well as the unfriendly gases. Still another popular sprayer is the air pump sprayer seen most frequently with insecticides and liquid garden products. The pump sprayer includes a hand operated air pump which is used to charge the container with compressed air. After it is charged, it operates much like an aerosol can. The pump sprayer is environmentally friendly but requires considerable effort to keep charged because air is not as efficient a propellant as environmentally unfriendly gases such as FREON or hydrocarbon gasses.
In recent years there has been some experimentation with battery powered pump sprayers. Most of these devices include a spray mechanism which is similar to the ubiquitous push button (or trigger) pump sprayer but which is coupled to a battery powered electric motor by some type of linkage which converts the rotary action of the motor into an oscillatory motion to drive the pump piston. Many of these battery operated pump sprayers are designed to work only with a specially constructed bottle, i.e. they are not retrofittable to existing pump spray bottles. Many also have weight distribution problems, i.e. they cause the bottle to which they are attached to tip over. Many of these battery powered pumps have large priming volumes, thus causing a delay between the time the pump is activated and the time liquid begins to be dispensed. Significantly, these pumps do not really provide a constant spray. They provide a continuous pulsed spray like that obtained by repeatedly squeezing the trigger or pushing the button on a hand operated spray pump. This is apparently one reason why such battery operated sprayers have not had commercial success.
Parent application Ser. No. 11/034,600 discloses a battery operated spray pump which includes a piston pump having a double end cam which is pushed by a pair of rotating cam pushers coupled to the electric motor via a gear transmission. The double end cam has an unequal duty cycle, i.e. takes more time to expel fluid from the piston cylinder than it takes to fill the cylinder. The cam pushers rotate at a speed which, in conjunction with the duty cycle of the cam, produces a low pressure nearly constant stream. According to the presently preferred embodiment, the duty cycle of the cam is approximately 270° and the speed of the cam pushers is approximately three rpm.
While the battery operated pump sprayer of the parent application provides significant improvement over the art, in order to obtain commercial success, not only do the pumping issues need to be addressed, but other issues regarding the batteries need to be properly addressed. For example, it is important that the battery cover protect the batteries from liquids. It is also important that the battery cover not easily detach unintentionally.